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| |
| <document> |
| |
| <properties> |
| <title>Commons SCXML Usage - API notes - EL</title> |
| <author email="commons-dev@jakarta.apache.org">Commons Documentation Team</author> |
| </properties> |
| |
| <body> |
| |
| <section name="Commons SCXML - Trying out EL without the servlet container"> |
| <p>Someone asked about Commons EL:<br/> |
| "<i>Is there no way to test this stuff outside of a Servlet/JSP |
| container?</i>"</p> |
| |
| <p>Commons SCXML supports EL as an expression language that may be used |
| within the expressions in an SCXML document. As a side-effect, a simple |
| API may be available for anyone who has the need to test without wanting |
| to deal with a Servlet/JSP container. <i>We understand this has limited |
| use.</i> |
| </p> |
| |
| <p>To test an expression language implementation, one minimally needs a |
| context of evaluation and an evaluator, which gives us the following |
| usage:</p> |
| <pre> |
| //import org.apache.commons.scxml.Context; |
| //import org.apache.commons.scxml.Evaluator; |
| //import org.apache.commons.scxml.SCXMLExpressionException; |
| //import org.apache.commons.scxml.env.jsp.ELContext; |
| //import org.apache.commons.scxml.env.jsp.ELEvaluator; |
| |
| Context context = new ELContext(); |
| // Say we have an instance 'foo' of type Foo which |
| // has a property 'bar' of type String |
| context.set("foo", foo); |
| |
| Evaluator evaluator = new ELEvaluator(); |
| |
| String bar = null; |
| try { |
| bar = (String) evaluator.eval(context, "${foo.bar}"); |
| } catch (SCXMLExpressionException see) { |
| // Commons SCXML wraps the underlying exception, |
| // in this case, a javax.servlet.jsp.el.ELException |
| } |
| </pre> |
| </section> |
| |
| </body> |
| |
| </document> |
